This invention relates generally to diagnostic imaging systems, and more particularly, to methods and apparatus for 4D image acquisition and analysis in an ultrasound protocol examination.
Ultrasound methods and systems exist for use in image data acquisition and medical diagnostics. These methods and systems can acquire ultrasound data and volume render the three-dimensional (3D) images for display, which is often referred to as ultrasound volume imaging. The 3D images also may be combined in time to produce a moving 3D image, which is often referred to as 4D ultrasound imaging. Thus, 4D ultrasound imaging adds the dimension of time to 3D volume imaging, thereby allowing the visualization of anatomy moving in real-time.
Various features have been proposed to facilitate patient examination and diagnosis based on ultrasound images of a patient. For example, in protocol based medical imaging examinations, such as stress-echo type heart studies, portions of the heart may be scanned before and after a stress test to provide corresponding base-line and stress-level images of the selected portions of the heart. In this type of study the patient's heart rate is increased by applying stress (typically physical or pharmacological stress) to the patient, and thereafter there is a limited time to acquire the necessary imaging projections of the heart.
In 4D imaging, it is possible to acquire over time images of the entire organ under investigation with the information needed for analysis extracted at a later time. In many cases, the images in the protocol have some type of relation. For example, a set of images may be acquired in order to show at different times (e.g., image of a heart under different stress levels at different times) the same projection or orientation relative to the organ under investigation. In such instances, the image acquisition setup should be the same at all stages of the imaging protocol. This consistent setup and acquisition will facilitate later comparison of the images to show changes in the organ under investigation. Moreover, in certain examinations, such as a stress-echo protocol examination, acquisition of different images of the heart should occur over a short time period of time in order to image the heart at the different stress levels.
Thus, in order to properly analyze acquired images, different images acquired over time for a particular protocol must be aligned. In 4D imaging it is particularly important to ensure the same geometric orientation of all acquired volume images over different time periods. Failure to properly align the volume images can result in difficulty in analysis and improper diagnosis. Additionally, in stress-echo examinations, if the imaging is not performed in a short enough time period, lower sensitivity of the examination may result, for example, due to some myocardial segments not being properly evaluated at a peak stress level.